An hour after seeing his post, the "Mama's Broken Heart" singer tweeted back, "Thanks for a great 2…well 8 years!" The country superstars dated for nearly five years before Shelton proposed on May 9, 2010.

Indeed, the couple's country love story marriage does seem like it's been a lot longer than two years. Constantly battling gossip and chatter -- specifically on Shelton's flirty ways -- the pair say they're in it for the long haul.

While Lambert, 29, told Us Weekly in April that they keep their union strong by talking "at least once a day, and we text a lot," Shelton, 36, laughed off any talk of rough waters that same month during a visit to "CBS This Morning."

"I just don't think my fans either are buying into it or have time to give a crap -- who has time to care these days?" the "Sure Be Cool If You Did" singer said of all the rumors.

Of his wife, he added, "I don't know that I ever really had any doubts. We had our ups and downs for damn sure along the way. I just could not imagine her not being in my life, I just couldn't get over her, I know I can't."

It's unclear how they plan on celebrating on Tuesday night, with Shelton filming The Voice in LA and Lambert on the road for her Four The Record tour, where she's due to perform in Phoenix, Ariz. on Thursday, May 16.

They did, however, share a special moment during her tour stop in Bakersfield, Calif. on Thursday, May 9, where her hubby surprised the crowd and sung his single "Boys 'Round Here" as Lambert lovingly looked on.

Of their 2011 nuptials that took place at the 125-acre Don Strange Ranch in Boerne, Tex., with 550 guests, including Reba McEntire, Cee Lo Green, andKelly Clarkson, Lambert recalls the day fondly.

"I'm married to my best friend!" she told Us after saying "I do." "Looking forward to a lifetime of laughter."

Two years later, Lambert gushes that she and Shelton are still very much in love.

"Like I always say, my mom said to my dad, 'Divorce is not an option,'" she told reporters at the 2013 Academy of Country Music Awards in April. "So we really love each other and have a real marriage outside of all of this. When this is all said and done, we will be drinking a beer together on a front porch somewhere, reminiscing about the good old days. That's what I'm happy about."